Optimization of high resolution digitally encoded laser scanners for fine feature marking

ABSTRACT

Disclosed herein are laser scanning systems and methods of their use. In some embodiments, laser scanning systems can be used to ablatively or non-ablatively scan a surface of a material. Some embodiments include methods of scanning a multi-layer structure. Some embodiments include translating a focus-adjust optical system so as to vary laser beam diameter. Some embodiments make use of a 20-bit laser scanning system.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/323,954, filed Jul. 3, 2014.

U.S. patent application Ser. No. 14/323,954 is a continuation-in-part ofU.S. patent application Ser. No. 14/030,799, and PCT Application No.PCT/US2013/060470, both filed Sep. 18, 2013, both of which claimpriority to U.S. Provisional Patent Application Nos. 61/818,881, filedMay 2, 2013, and 61/767,420, filed Feb. 21, 2013.

U.S. patent application Ser. No. 14/323,954 is a continuation-in-part ofPCT Application No. PCT/US2014/017841, filed Feb. 21, 2014, which claimspriority to U.S. Provisional Patent Application Nos. 61/818,881, filedMay 2, 2013, 61/767,420, filed Feb. 21, 2013, and 61/875,679, filed Sep.9, 2013.

U.S. patent application Ser. No. 14/323,954 is a continuation-in-part ofPCT Application No. PCT/US2014/017836, filed Feb. 21, 2014, which claimsthe benefit of U.S. patent application Ser. No. 14/030,799, filed Sep.18, 2013, and U.S. Provisional Patent Applications Nos. 61/818,881,filed May 2, 2013, and 61/767,420, filed Feb. 21, 2013.

U.S. patent application Ser. No. 14/323,954 claims the benefit of U.S.Provisional Patent Application No. 61/875,679, filed Sep. 9, 2013.

The prior application Ser. No. 14/323,954, PCT/US2013/060470,PCT/US2014/017836, PCT/US2014/017841, Ser. No. 14/030,799, 61/818,881,61/767,420, and 61/875,679, are hereby incorporated herein by referencein their entireties.

FIELD

The present disclosure relates generally to laser patterning, and moreparticularly to optimization of high resolution digitally encoded laserscanners for fine feature marking.

BACKGROUND

Strong demand for smaller and more portable computing devices has led tosubstantial innovation in many corresponding areas, including touchscreens for smartphones and tablet computers. However, there remainsmuch room for improvement in the area of touch sensor patterning andprinted electronics. Existing technologies, including photolithography,screen printing, and laser processing, suffer from various drawbacks duein part to the number of processing steps required and the costs andtime consumed in switching between various processing steps. In additionto costs associated with various processing steps, photolithographic andscreen printing techniques include numerous drawbacks, includingincreased cost associated with expensive consumables and toxic waste.Conventional laser processing techniques also suffer from numerousdrawbacks. It is unfortunate that the current state of the art has yetto produce more efficient methods and systems for processing printedelectronics and touch sensors. Accordingly, there remains a need forimproved methods and systems for processing these devices without theattendant drawbacks.

SUMMARY

The present disclosure is directed to satisfying the aforementioned needby providing an innovation in the form of laser processes which changethe conductivity of a surface of a substrate without ablating thematerial thereof. Thus, according to one aspect of the presentdisclosure, a method is provided for processing a transparent substrate,the method including the steps of generating at least one laser pulsehaving laser parameters selected for non-ablatively changing aconductive layer disposed on the transparent substrate into anon-conductive feature, and directing the pulse to the conductive layer.

In some embodiments, the laser parameters include a pulse length of lessthan about 200 ps and a pulse fluence of less than about 1.5 J/cm². Insome embodiments, a spot size of the pulse is varied within a range of 5to 100 μm by varying the position of the substrate in relation to theincident pulse. In some embodiments, the transparent substrate includesa protective film disposed on a surface of the substrate opposite fromthe conductive layer, and which protective film is not removed duringthe non-ablative processing of the conductive layer. In someembodiments, the transparent substrate is made of a flexiblepolyethylene terephthalate material. In some embodiments, to an unaidedeye of an observer the non-conductive feature is visiblyindistinguishable or has very low visibility as compared to an adjacentunprocessed conductive layer. In some embodiments, the pulse is directedthrough the transparent substrate to the conductive layer. In someembodiments, the conductive layer includes silver nanowires. In someembodiments, the surface roughness of the conductive layer issubstantially unchanged after processing with the laser pulse. In someembodiments, the conductive layer becomes non-conductive in theprocessed area through a selective oxidation mechanism.

In another aspect of the present disclosure, a method is provided forchanging the sheet resistance of a conductive matrix of silver nanowireson a flexible transparent substrate, the method including generating atleast one pulse with laser parameters selected in a range for increasingthe sheet resistance of the conductive matrix without ablating thesilver nanowires, and directing the pulse to the conductive matrix toincrease the sheet resistance. In some embodiments, the flexibletransparent substrate includes a protective film disposed on a surfaceof the substrate opposite from the conductive matrix of silvernanowires, and which protective film is not removed during thenon-ablative processing of the conductive matrix by the laser pulse. Insome embodiments, to an unaided eye of an observer an area processed bya plurality of the laser pulses is visibly indistinguishable or has verylow visibility as compared to an adjacent unprocessed area.

In a further aspect of the present disclosure, a method is provided forprocessing a transparent substrate with a pulsed laser beam, thesubstrate being characterized by having a conductive material disposedon a selected surface thereof, the conductive material capable ofexperiencing non-ablative change into non-conductive material with apulsed laser beam having selected parameters, the method including thesteps of generating at least one laser pulse with the selectedparameters, and directing the pulse to the conductive material on thesubstrate to produce the change into non-conductive material.

In some embodiments, the transparent substrate includes a protectivefilm disposed on a surface of the substrate opposite from the conductivematerial, and which protective film is not removed during thenon-ablative processing of the conductive material. In some embodiments,to an unaided eye of an observer the non-conductive material is visiblyindistinguishable or has very low visibility as compared to unprocessedconductive material.

In a further aspect of the present disclosure, a method is provided forprocessing a conductive material layer of a flexible transparentsubstrate with a pulsed laser beam, the conductive material layercharacterized in that exposure to a laser pulse having selected laserpulse parameters causes the conductive material to become non-conductivematerial without ablatively removing the material layer, the methodincluding the steps of generating at least one laser pulse which has theselected laser pulse parameters, and directing the pulse to theconductive material layer of the substrate. In some embodiments theconductive material layer includes silver nanowires.

In another aspect of the present disclosure target surfaces can beprocessed with laser pulses such that processed areas are not visuallydistinguishable from adjacent unprocessed areas except under substantialmagnification. In another aspect of the present disclosure, a protectivelayer typically disposed on a surface of the substrate to be processedand removed during processing is instead left intact and not removedfrom the substrate during processing.

According to one aspect of the present disclosure, a method of laserpatterning a multi-layer structure, the multi-layer structure includinga substrate, a first layer disposed on the substrate, a second layerdisposed on the first layer, and a third layer disposed on the secondlayer, includes generating at least one laser pulse having laserparameters selected for non-ablatively changing the conductivity of aselected portion of the third layer such that the selected portionbecomes non-conductive, and directing the pulse to the multi-layerstructure, wherein the conductivity of the first layer is notsubstantially changed by the pulse.

In some embodiments, the first layer and third layer include silvernanowires. In some embodiments, the first layer includes ITO. In someembodiments, the second layer is a photoresist with insulationproperties. In some embodiments, the second layer is configured toprotect the first layer from conductivity altering characteristics ofsaid pulse. In some embodiments, the second layer is configured toscatter or absorb energy from said pulse. In some embodiments, the firstlayer has a higher conductivity alteration threshold than the thirdlayer. In some embodiments, the first layer has been heat treated so asto increase the conductivity altering threshold thereof.

In another aspect of the disclosure a method of forming a multi-layerstack-up structure includes providing a substrate, depositing a firstlayer on the substrate, the first layer being conductive, laserpatterning the first layer such that selected portions of the firstlayer become non-conductive, depositing a second layer on the firstlayer, the second layer being insulating, depositing a third layer onthe second layer, the third layer being conductive, and non-ablativelylaser patterning the third layer such that selected portions of thethird layer become non-conductive without substantially changing theconductivity of the first layer.

In some embodiments, the first and third layers include silvernanowires. In some embodiments, the first layer includes ITO. In someembodiments, the second layer is photoresist with insulation properties.In some embodiments, the second layer is configured to protect the firstlayer from changing conductivity during the non-ablative laserpatterning of the third layer. In some embodiments, the second layer isconfigured to scatter or absorb energy during the non-ablative laserpatterning of the third layer. In some embodiments, the first layer hasa higher conductivity alteration threshold than the third layer. In someembodiments, the method further comprises the step of heat treating thefirst layer after the first layer has been laser patterned. In someembodiments, the laser patterning of the first layer is non-ablative.

In some embodiments, an optical processing system comprises an objectivelens situated to direct a processing optical beam to a target surfaceand a scanning system situated to scan the processing optical beamacross the target surface. A focus-adjust optical system includes afocus-adjust optical element and a focus actuator, the focus-adjustoptical element situated to direct the optical beam to the objectivelens. The focus actuator is coupled to the focus-adjust optical elementso as to translate the focus-adjust optical element along an axis of theobjective lens so as to maintain a focus of the processing beam as theprocessing beam is scanned across the target surface. A beam diameteractuator is situated to translate the focus-adjust optical system so asto define a processing beam diameter at the target surface. In someexamples, a controller is coupled to the focus actuator so as tomaintain the focus of the processing beam during scanning across thetarget surface. In other examples, a substrate stage includes a stageactuator situated to position the target surface along the axis of theobjective lens. In further examples, the controller is coupled to thebeam diameter actuator and the stage actuator and the controllertranslates the focus adjust optical system and the substrate stage basedon a selected beam diameter. In a particular example, the beam diameteractuator produces stepwise translations of the focus adjust opticalsystem, and is translatable to at least two locations along the axis ofthe objective lens, the at least two locations associated withcorresponding focused beam diameters having a larger to smaller diameterratio of at least 2:1, 3:1, 4:1, 5:1, 7.5:1, or 10:1. Typically, thebeam diameter actuator is situated to translate the focus-adjust opticalsystem so as to define at least two processing beam diameterscorresponding to ablative processing and non-ablative processing ofsilver paste conductive borders, and silver nanowire or indium tin oxideconductive layers, or vice versa. In some examples, a laser produces theprocessing beam, and a laser controller selects optical beam powersbased on the processing beam diameters. In some examples, the focusactuator is coupled to the focus-adjust optical element so as totranslate the focus-adjust optical element along the axis of theobjective lens so as to compensate for field curvature of the objectivelens.

Methods include translating a focus adjust optical element along an axisof an objective lens while processing a substrate with an optical beamfrom the objective lens so as to maintain a processing beam focus at atarget. A processing beam diameter is selected by translating the focusadjust optical element along the axis of the objective lens. In someexamples, processing beam diameter is selected from among at least twopredetermined values, wherein the predetermined values have a larger tosmaller diameter ratio of at least 1.5:1. In other examples, the targetis a composite having a conductive layer and a conductive border,wherein the at least two predetermined values include first and secondprocessing beam diameters selected for processing the conductive layerand the conductive border, respectively. In additional examples, thefirst and second processing beam diameters are selected so that theconductive layer is processed non-ablatively and the conductive borderis processed ablatively or vice versa. In typical applications, theprocessing beam diameters are selected to process one or more of asilver nanowire or indium tin oxide conductive layer and a silver pasteconductive border. In some embodiments, the target is translated alongthe axis of the objective lens based on the selected processing beamdiameter. In a representative example, at least two processing beamdiameters are selected for processing a conductive layer and aconductive border of a composite substrate, wherein the processing beamdiameters are selected from among at least two predetermined values,wherein the predetermined values have a larger to smaller diameter ratioof at least 2:1. In some examples, the first and second processing beamdiameters are selected so that the conductive layer is processednon-ablatively and the conductive border is processed ablatively or viceversa. In some examples, a method further comprises selecting first andsecond optical beam powers corresponding to the first and secondprocessing beam diameters.

In some embodiments, a method comprises receiving a pattern descriptionstored in at least one computer readable storage medium, the patterndescription comprising a definition of at least one pattern featureassociated with a scan vector, and directing a laser beam over a fixedscan area based on the pattern description, wherein the laser beam isdirected over the scan area with a transverse displacement resolutionthat is less than 1/20 of a laser beam diameter.

In some embodiments, a method comprises selecting a laser beam diameter,situating a substrate to be scanned at a scan plane associated with theselected laser beam diameter, and exposing the substrate to a laser beamwith the selected laser beam diameter by scanning the laser beam withrespect to the substrate, wherein the laser beam is scanned with angularscan increments corresponding to less than 1/10 of the laser beamdiameter at the scan plane.

In some embodiments, an apparatus comprises a laser configured toproduce a processing beam, an optical system, and a scan controllerconfigured to receive a scan pattern defined as a plurality of scanvectors and configured to control the optical system to direct theprocessing beam to a scan area with a predetermined beam diameter. Insome cases, the scan controller is configured to control the opticalsystem to scan the processing beam with respect to the scan area so asto produce an exposed scan vector such that a transverse offset betweenthe exposed scan vector and an intended scan vector is less than 1/10 ofthe predetermined beam diameter.

The foregoing and other objects, features, and advantages of thedisclosure will become more apparent from the following detaileddescription, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of laser beam processing a substrate inaccordance with an aspect of the present disclosure.

FIG. 2 is a flowchart block diagram of a method in accordance with anaspect of the present disclosure.

FIG. 3 is a top view image of a laser beam patterned substrate inaccordance with an aspect of the present disclosure.

FIG. 4 is an image with overlaid profilometer data of unprocessed andprocessed areas in accordance with an aspect of the present disclosure.

FIGS. 5A and 5B are XPS plots of unprocessed and processed areas,respectively, in accordance with an aspect of the present disclosure.

FIG. 6 is an XPS plot of selected species from the plot in of FIG. 5B.

FIGS. 7A-7C show cross-sections of an exemplary stack-up structure atvarious steps in fabrication, in accordance with an aspect of thepresent disclosure.

FIGS. 8A-8C show cross-sections of an exemplary stack-up structure atvarious steps in fabrication, in accordance with another aspect of thepresent disclosure.

FIGS. 9A-9C show cross-sections of an exemplary stack-up structure atvarious steps in fabrication, in accordance with another aspect of thepresent disclosure.

FIG. 10 shows an exemplary laser-based processing system.

FIG. 11 illustrates displacements associated with beam diameteradjustment.

FIG. 12 shows a composite material being processed with a system such asillustrated in FIG. 10.

FIG. 13 illustrates focal regions associated with different beamdiameters.

FIG. 14 shows a method of processing a composite material.

FIG. 15 shows an exemplary processing system that includes a controlsystem and a laser scanning system.

FIG. 16 shows an exemplary computing environment configured to controlsubstrate processing with focus control and beam diameter adjustment.

FIG. 17 illustrates a representative assembly for adjusting beamdiameter.

FIG. 18 illustrates a laser scanning system and three focal planes.

FIGS. 19A and 19B each illustrate an input pattern and a patternactually scanned by a laser scanning system.

FIGS. 20A and 20B each illustrate several lines scanned by a laserscanning system.

FIG. 21 illustrates an input pattern for a laser scanning system.

FIG. 22 illustrates an exemplary method.

DETAILED DESCRIPTION I. General Considerations

As used in this application and in the claims, the singular forms “a,”“an,” and “the” include the plural forms unless the context clearlydictates otherwise. Additionally, the term “includes” means “comprises.”Further, the term “coupled” does not exclude the presence ofintermediate elements between the coupled items.

The systems, apparatus, and methods described herein should not beconstrued as limiting in any way. Instead, the present disclosure isdirected toward all novel and non-obvious features and aspects of thevarious disclosed embodiments, alone and in various combinations andsub-combinations with one another. The disclosed systems, methods, andapparatus are not limited to any specific aspect or feature orcombinations thereof, nor do the disclosed systems, methods, andapparatus require that any one or more specific advantages be present orproblems be solved. Any theories of operation are to facilitateexplanation, but the disclosed systems, methods, and apparatus are notlimited to such theories of operation.

Although the operations of some of the disclosed methods are describedin a particular, sequential order for convenient presentation, it shouldbe understood that this manner of description encompasses rearrangement,unless a particular ordering is required by specific language set forthherein. For example, operations described sequentially may in some casesbe rearranged or performed concurrently. Moreover, for the sake ofsimplicity, the attached figures may not show the various ways in whichthe disclosed systems, methods, and apparatus can be used in conjunctionwith other systems, methods, and apparatus. Additionally, thedescription sometimes uses terms like “produce” and “provide” todescribe the disclosed methods. These terms are high-level abstractionsof the actual operations that are performed. The actual operations thatcorrespond to these terms will vary depending on the particularimplementation and are readily discernible by one of ordinary skill inthe art.

In some examples, values, procedures, or apparatus' are referred to as“lowest”, “best”, “minimum,” or the like. It will be appreciated thatsuch descriptions are intended to indicate that a selection among manyused functional alternatives can be made, and such selections need notbe better, smaller, or otherwise preferable to other selections.

For convenient description, terms such as “top,” “upper,” “lower,”“bottom” and the like are used to describe certain features of thedisclosed embodiments. Such terms are not intended to refer to aparticular orientation, but are instead used to indicate relativepositions.

As used herein, laser beam diameters are generally based on 1/e²intensities for a lowest order TEM₀₀ mode or similar power distribution.The terms “axis” or “optical axis” refer to axes coupling opticalelements. Such axes need not be a single straight line segment, but caninclude a plurality of line segments corresponding to bends and foldsproduced with mirrors, prisms, or other optical elements. As usedherein, a lens refers to single lens element or multi-element (compound)lenses.

II. Non-Ablative Laser Patterning

Flexible substrates have the advantage of potentially being inexpensiveto manufacture, though such efficiencies have not been realized underconventional processes. Accordingly, various examples described hereinare directed to the manufacture of processed composite films fordifferent applications, such as transparent conductors fortouch-sensitive displays. For example, steps for processing the flexiblecomposite films can be configured so that touch sensitive regions areformed in the flexible composite film such that the touch sensitiveregions become suitable for use in various display devices. Othersuitable applications for processed substrates can include displaydevices more generally, as well as LED phosphor enhancements, othercommercial and consumer lighting applications, wearable electronics, andphotovoltaic cells. However, flexible substrates are particularlywell-suited for mobile consumer displays, where thinner, durable, andflexible formats are highly desirable. Moreover, by utilizing theadvances described herein, flexible film laser patterning can beachieved with an intact protective layer, enabling true roll to rollprocessing. In some examples, the substrate can be rigid as well.

Referring now to FIG. 1, a cross-sectional view is shown of a pulsedlaser beam 1010 with selected laser pulse parameters processing a target1012 in accordance with an aspect of the present disclosure. As shownthe target 1012 includes a transparent substrate 1014 having aprotective layer 1016 disposed on one side and thin layer 1018 ofconductive material disposed on the other side opposite from the oneside. In many examples, the substrate 1014 has a constant or fixedthickness, such as in the range between 50 μm and 200 μm, usuallydepending upon the application for the substrate and material ormaterials used. In further examples, additional layers may be disposedin relation to the substrate 1014 and associated protective and thinlayers 1016, 1018, such as the formation a composite substrate or asubstrate with one or more other materials or layers deposited thereon.

In some examples the layer 1018 of conductive material includes a randomarrangement of silver nanowires. The silver nanowires of the thin layer1018 are typically secured to the substrate 1014 in a polymer matrix,such as an organic overcoat. The laser beam 1010 delivers laser pulsesto the thin layer 1018 and creates a processed portion 1020 where theconductivity of the material of layer 1018 changes substantially.Herein, the terms “conductive” and “non-conductive” have meaningsattributed to them that are generally understood in the art of printedelectronics, touch sensor patterning, or optoelectronics, as set forthin greater detail below.

FIG. 2 shows a flowchart block diagram of an exemplary method 1100 inaccordance with an aspect of the present disclosure. In a first step1102, a substrate is provided with a thin conductive layer disposedthereon. The substrate is preferably transparent and flexible, but othersubstrates can be processed in accordance herein without departing fromthe scope of the present disclosure. In accordance with another aspectof the present disclosure, a protective layer or film can be disposed onanother surface of the substrate, for example, opposite from theconductive layer and the substrate can be processed without removing theprotective layer or film. In a second step 1104, at least one laserpulse is generated with laser pulse parameters selected for achievingnon-ablative processing of the thin conductive layer on the substratesuch that the processed portion of the thin conductive layer becomesnon-conductive, and such that the processed portion is also lowvisibility. In a third step 1106, the at least one laser pulse isdirected to the substrate. The processed substrate has a differentconductivity than the unprocessed substrate such that particular sensingregions and electrical pathways may be formed on the substrate. Bycarefully selecting the characteristics of the laser pulse, includingpulse parameters such as pulse length, pulse fluence, pulse energy, spotsize, pulse repetition rate, and scan speed, the substrate may beprocessed such that electrical characteristics thereof are altered in apredetermined way while the substrate and associated protective andconductive layers are not substantially damaged or structurally alteredthrough an ablative process. Accordingly, a protective layer (forexample, the protective layer 1016) need not be removed duringprocessing of the substrate in examples utilizing such a layer.

While the beam 1010 in FIG. 1 is generally shown being brought to afocus thereof, other beam geometrical configurations and intensitydistributions are possible, including an unfocused beam, line beams,square or rectangular beams, as well as beams with uniform,substantially uniform or preselected intensity profiles across one ormore transverse axes. In some examples, the beam delivery systemproviding the beam 1010 is also configured to translate the beam 1010 inrelation to the target 1012 so that the beam can form lines, areas, andother geometrical features thereon. In other examples, the target 1012can be translated to form geometrical features while the beam deliverysystem and beam 1010 remain fixed in one or more axes. In still otherexamples, both the target 1012 and the beam 1010 can be translated.Moreover, in some examples, the beam 1010 impinges the target 1012 fromthe opposite direction such that the beam 1010 propagates through theprotective layer 1016 (if present) and substrate 1014 to causenon-ablative effects to the conductive layer 1018.

As used herein, ablative processing is understood to mean substantialremoval of material from a target caused by an incident optical beam byvaporization, photochemical alteration, or otherwise. Similarly,non-ablative processing is understood to mean that the structuralfeatures of the existing target surface topology remain intact afterprocessing, even if electrical or other properties of the target arechanged. In some examples, a non-ablatively processed surface can bevisually indistinguishable from an adjacent unprocessed area. In someexamples, non-ablative processing of silver nanowires does not remove orsubstantially remove the silver nanowires. An overcoat covering thesilver nanowires can be removed from the silver nanowires through laserprocessing without the process being considered ablative with respect tothe silver nanowires.

While the laser pulses of the laser beam 1010 cause the processedportion 1020 to become non-conductive, the visible characteristics ofthe processed portion 1020 remain substantially unchanged. Thus, thedistinction between processed and unprocessed portions 1020, 1018 isunnoticeable without the aid of an image enhancement mechanism, such asa microscope, including across multiple viewing angles. Referring toFIG. 3, a microscope image is shown, magnified to 1500× undermonochromatic illumination, of a top view of a substrate (such as thesubstrate 1014) processed in accordance with a representative disclosedmethod. A horizontal stripe 1022 of processed silver nanowires, which isbarely noticeable to an unaided eye even under substantialmagnification, is shown that is approximately 30 μm wide, as indicatedin FIG. 3. The laser pulse parameters used to provide superiornon-ablative results shown in the stripe 1022 include a pulse length ofabout 50 ps, a pulse fluence of about 0.17 J/cm², a spot size of about40 μm 1/e², a scan rate of about 1 m/s with a pulse-to-pulse overlap ofgreater than 90%, a total pulse energy of about 12 μJ, and a pulserepetition rate of about 100 kHz.

The aforementioned laser pulse parameter values are merely examples, andother parameters may be selected and optimized for different targets andsystems. Additionally, parameter values can be scaled for a variety ofprocessing speeds, provided pulse overlap and pulse energy aremaintained in parameter ranges suitable for producing non-ablativenon-conductive effects. Thus, pulse repetition rates can be increased to1 MHz, 10 s of MHz, or more to increase processing speeds provided therequisite laser and beam delivery architectures are configuredaccordingly. Pulse length can be selected to be shorter or longer andother parameters, such as pulse fluence, can be adjusted to ensure thattarget is processed non-ablatively into a non-conductive feature. Forexample, possible pulse lengths include less than about 1 ps, 100 ps,200 ps, 500 ps, 800 ps, or 1 ns. Other parameters can similarly bevaried and optimized accordingly.

After formation, the two portions of the target 1012 above and below thestripe 1022 become electrically isolated from each other due to thechange in sheet resistance imparted to the processed area 1020 by thepulses from the laser beam 1010, effectively forming a barrier toconductive flow of electricity. As material specifications change, otherparameters can be carefully selected using heuristic or otheroptimization approaches to achieve the non-ablativeconductivity-altering aspects of the processes of the present disclosurewhile maintaining ultra-low visibility of the processed area as comparedto unprocessed areas. The laser beam 1010 can also be modified to have ashape other than Gaussian, such as flat-top, super-Gaussian, etc. Lasersystems capable of operating the laser parameter regime of the presentdisclosure generally include pulsed fiber lasers, pulsed fiberamplifiers, and diode pumped solid-state lasers.

Accordingly, shapes and patterns can be formed on the substrate with themethods disclosed herein so as to achieve electrical isolation from oneunprocessed area to the next. In addition to not requiring a mask,photoresists, etch baths, replacing or providing additional protectivefilms, the use of a laser or a scanned laser provides a highlyconfigurable process, allowing for sheet-to-sheet, roll-to-sheet,roll-to-roll (R2R), or roll to finished sensor manufacturing. Scannedlasers can be programmed with an image file to have the process tailoredeasily for or between various pattern geometries and substrates.Moreover, by utilizing the ultra-low visibility process aspectsdescribed herein, even more reductions in cycle time can be achievedover conventional laser or chemical processes. For example, in aconventional laser process, in order to reduce the visibility ofablatively processed areas, additional areas must be unnecessarilyprocessed in order to provide a uniform pattern effect that effectivelydecreases the overall visibility of the ablative marks to the unaidedeye of a user. Because the processing aspects of the present disclosureresult in ultra-low visibility marks to begin with, the additionalprocess time associated with filling in areas to decrease visibility isno longer necessary, resulting in a quicker and hence more costeffective process.

The transparent substrate 1014 can be composed of a variety of differentmaterials, including glass, plastic, or metal. Typical substrates tendto be made of polyethylene terephthalate (PET) because of its low costand advantageous features, including transparency, flexibility,resilience, ease of manufacture, etc. PET substrates can be manufacturedusing one or more ways known to those with skill in the art oftransparent conductive film processing, and which in some examples canbe provided in a roll suitable for roll-to-roll processing. Anon-exhaustive list of other possible substrate materials includesglass, polyethylene naphthalate, polyurethane, and various metals. Thesubstrate 1014 shown in FIG. 3 has a thickness of about 0.13 mm and ismade of polyethylene terephthalate. In this thickness range, PET alongwith other suitable materials are flexible and can be stored,transported, or configured for processing in a roll of predeterminedwidth. The substrate 1014 is typically transparent for visual displayapplications such that when the substrate 1014 is later applied to adisplay device (not shown), light from the display device may propagatethrough the substrate 1014 towards a user of the device.

In typical examples of flexible transparent conductive films, roughstock is provided in a roll or in a flat sheet configuration for laserpattern processing of the transparent conductive film so that the roughstock becomes processed stock suitable for use in various applications,such as optoelectronic devices. In some examples, transparent conductivefilm material includes silver nanowires (also referred to as SNW orAgNW) deposited to a predetermined thickness or conductivity, both ofwhich are typically set by increasing or decreasing the density of thesilver nanowires in the film production phase. In other examples,transparent conductive film can include other materials or with multiplelayers. Transparent conductive films can find end use on rigid surfaces,for example on rigid glass or composite screens. Silver nanowires arewell-suited for flexible substrates, as material properties thereof,such as conductivity and structural integrity, are more consistent underbending loads of various types (e.g., fixedly curved, cyclicallydeformed, or pliable).

The protective layer 1016 can also be made of different materialssuitable for providing protection from damage due to particulate matter,scuffs, and scratches. The thickness of the protective layer 1016 istypically selected to be suitable for providing protection to theunderlying substrate 1014. One suitable thickness is approximately 0.04mm, however other thicknesses may be used. Since aspects of the presentdisclosure can eliminate the need for removing, reapplying, or replacingthe protective layer 1016 during manufacture, protective layers 1016comprising various materials may be possible. Protective films 1016 madefrom polyethylene or polyethylene terephthalate are suitable forproviding the requisite protection of the surface of the substrate 1014.The requirements in conventional processes that protective layers suchas the protective layer 1016 must be removed before and reattached orreapplied after processing the substrate 1014 to avoid damage to theprotective layer resulting from intense heat imparted by the laserduring processing leads to substantial additional processing time andcost. As disclosed herein, a substrate 1014 can be processed withoutremoval and reattachment or reapplication of the protective layer 1016,leading to the potential for revolutionary cost reduction in processingof transparent substrates, including flexible transparent substrates.

FIG. 4 is a similar image of a top view of a target substrate 1014 asshown in FIG. 3, with additional surface roughness data superimposedthereon. A first horizontal line 1024 extends approximately along amiddle of the processed stripe 1022. About 30 μm adjacent to firsthorizontal line 1024, a second horizontal line 1026 extends paralleltherewith along an unprocessed area 1018. An area 1028 on the bottom ofthe image includes the transverse depth profiles 1030, 1032 along therespective parallel lines 1024, 1026. The depth profiles are overlaid onone another and show minimal variation with respect to each other in acommon range of approximately 0.2 μm of depth, further demonstrating thenon-ablative effects associated with processes in accordance withaspects of the present disclosure. Other surfaces may have a largerrange of depth variation depending on the quality of the substrate andconductive surface layer, however the variation between processed andunprocessed areas is minimal under the non-ablative processes herein.

FIGS. 5A and 5B show x-ray photoelectron spectroscopy (XPS) results forunprocessed (FIG. 5A) and processed (FIG. 5B) areas of a substrate 1014,indicating counts per second with respect to binding energy. The XPSgenerally assist in explaining the elemental content of targetedsurfaces and resulting material changes that may occur from variousexternal inputs. The results shown for unprocessed and processed areasare substantially the same across a range of binding energies, with someparticular exceptions. Binding energy peaks for AgMNN, Ag 3p3/2, Ag3p1/2, and Ag 3d, appear in processed areas 1020, generally indicatingthe presence of oxidized silver. For example, referring to FIG. 6, aplot of binding energy with respect to kinetic and photon energiescentered around 368 eV and generally indicates oxide formation in theprocessed area. Also, comparison of various carbon species, chlorine,fluorine, oxygen, and silicon signal data suggests that the polymermatrix in which the silver nanowires are embedded is present before andafter processing by the laser pulses. Thus, it is likely that organicovercoat is selectively removed from the silver nanowires, allowing thenanowires to become oxidized and exhibit a non-conductivecharacteristic, while the remainder of the overcoat remainssubstantially intact. In general, silver nanowires can exhibitattributes superior to more conventional transparent conductive filmslike Indium Tin Oxide (ITO). The transparent conductive layer 1018 istypically on the order of a few tens of nanometers thick. Silvernanowires tend to be approximately 10 μm long and in the range ofseveral to several tens of nanometers in diameter, though otherdimensions may be possible.

Laser parameters suitable for non-ablative laser processing inaccordance with the methods of the present disclosure can be selectedbased in part on the relevant properties of the materials selected to beprocessed. For example, varying thickness of the underlying substrate,the thin conductive layer, etc., can affect how laser pulse heat may bedistributed or result in other time-dependent effects requiringmitigation. The optimized process parameters will result in a processedarea or feature having ultra-low visibility as compared to adjacent orseparate unprocessed areas. One area of optimization can include laserpulse wavelength. The wavelength of light used to process samples shownin the images herein is 1064 nm, and is generally preferred since suchlonger wavelength light interacts with the transparent substrate,protective film, or other material or material layers in proximity, lessthan shorter wavelengths. Other techniques, such as photolithography,often require wavelengths which are more difficult or expensive toproduce, such as wavelengths in the visible or UV spectra.

By processing target substrates in accordance with methods herein,various advantages can be realized over conventional manufacturingtechniques for processing transparent substrates, as becomes apparent inlight of the present disclosure.

III. Laser Patterning of Multi-Layer Structures

Touch sensors typically comprise a film composite of various materialswhich become stacked together through one or more deposition orlamination processes. A variety of stack-up configurations is possible,and various intermediate processing steps can be implemented during thefabrication of the multiple layers. For example, different multi-layerstructures described herein can have layers arranged in a differentorder than as disclosed in the drawings. In some embodiments, depositedmaterial layers can be disposed on one or both sides of a substrate. Infurther embodiments, the pulsed laser beam can be incident from theopposite direction as shown. Different types of materials can be usedfor the different layers, the ones being discussed herein being somesuitable examples. It will be appreciated that many differentconfigurations and variations are possible that are within the scope ofthe present disclosure.

Reference is now made to FIGS. 7A-7C which depicts different stages formethods of non-ablative laser processing a multi-layer stack-up ofmaterials, in accordance with aspects of the present disclosure. In FIG.7A, a multi-layer stack-up structure 2010 is provided which includes asubstrate layer 2012, made of PET or other suitable material. Thestructure 2010 includes a conductive first layer 2014 disposed on thesubstrate layer 2012. The first layer 2014 includes silver nanowires, oranother suitable conductive material. A second layer 2016, which may bemade of photoresist or other suitable insulating material, is disposedon the first layer 2014. Before the insulating layer 2016 is depositedor formed on the first layer 2014, the structure 2010 can be laserprocessed non-ablatively to form selected non-conductive regions,including lines, patterns, or other geometries, the non-ablativeprocessing being described further hereinafter.

The insulating layer 2016 can include one or more dopants that increasethe ability of the layer 2016 to scatter or absorb incident laser energyso as to reduce the amount of residual fluence that is incident on thefirst layer 2014. In FIG. 7B a third layer 2018 is deposited or formedon the second layer 2016 of the multi-layer structure 2010. The thirdlayer will typically include silver nanowires, though other suitableconductive materials can be used if capable of non-ablative conductivityalteration. One preferred layering is silver nanowires in both the firstand third layers 2014, 2018. Silver nanowires offer several advantagesover other materials, including the ability to be laser processednon-ablatively (as disclosed herein) and their ability to retain theircharacteristics under deformation, such as bending loads. For example,silver nanowires are well-suited for application in flexible touchscreens. In FIG. 7C, a pulsed laser beam 2021 is generated havingprocess parameters suited for non-ablative alteration of the target. Thepulsed laser beam 2021 is directed to the structure 2010 for laserprocessing of the structure 2010. The pulsed beam 2021 interacts withthe third layer 2018 of structure 2010 without ablating a selectedportion 2022 of third layer 2018. Through the interaction with the laserpulses from the pulsed laser beam 2021 the conductivity of the selectedportion 2022 is changed to non-conductive. At the same time, a selectedportion 2024 of the first layer 2014 that is below the third layer 2018does not experience the same change in conductivity. Additionally, theselected portion 2024 is not ablated by the beam 2021. The insulatinglayer 2016 can assist in mitigating the pulse energy received by thefirst layer 2014 in order to prevent a conductivity altering-materialinteraction.

In FIGS. 8A-8C, another aspect is shown of a laser processing method ofa multi-layer stack-up structure 2020 in accordance with an aspect ofthe present disclosure. In FIG. 8A, a stack-up structure 2020 includes asubstrate 2012 and a first layer 2026, the first layer 2026 preferablyincluding silver nanowires. The first layer 2026 is heat treated,represented by the downward facing arrows to alter upward a conductivitychanging threshold characteristic of the first layer 2026. Thus, afterheat treatment, the threshold for alteration of the conductivity of thefirst layer 2026 is higher. In some examples, this conductivity alteringthreshold can be related to an ablation threshold of the material.Various temperatures for heat treatment can be used and the temperaturecan be selected or adjusted to provide different effects to the firstlayer 2026. In some examples heat treatment is performed with an oven, alaser, or other heat treating mechanism. The heat treatment of the firstlayer 2026 can result in an alteration in density of an organic overcoatcovering the silver nanowires in the first layer 2026, increasing thefluence threshold thereof. In FIG. 8B, the structure 2020 has undergonesubsequent layering steps, providing second layer 2016 on top of firstlayer 2026, and a third layer 2018 on top of second layer 2016. In FIG.8C, a pulsed laser beam 2021 is generated having process parameterssuited for non-ablative alteration of the target. The pulsed laser beam2021 is directed to the structure 2020 for laser processing of thestructure 2020. The pulsed beam 2021 interacts with the third layer 2018of structure 2010 without ablating a selected portion 2022 of thirdlayer 2018. Through the interaction with the laser pulses from thepulsed laser beam 2021 the conductivity of the selected portion 2022 ischanged to non-conductive. At the same time, a selected portion 2024 ofthe first layer 2026 that is below the third layer 2018 does notexperience the same change in conductivity. Additionally, the selectedportion 2024 is not ablated by the beam 2021.

With reference to FIGS. 9A-9C, an aspect is shown of a laser processingmethod of a multi-layer stack-up structure 2030 in accordance with anaspect of the present disclosure. In FIG. 9A, a stack-up structure 2030includes a substrate 2012 and a first layer 2028, the first layer 2028preferably including indium tin oxide. The first layer 2028 can beprocessed ablatively such that portions of the first layer 2028 areremoved through an ablative laser process. A second layer 2016 isdeposited on the first layer 2028. In FIG. 9B a third layer 2018 isdeposited or formed on the second layer 2016. Third layer 2018 isdifferent from the material composition of the first layer 2028, withthird layer 2018 preferably including conductive silver nanowires.Because of the material difference, the third layer 2018 has aconductivity changing threshold characteristic that is different fromthe first layer 2028. The structure 2030 is processed by a pulsed laserbeam 2021 in FIG. 9C. The pulsed laser beam 2021 is generated havingprocess parameters suited for non-ablative alteration of the target. Thepulsed laser beam 2021 is directed to the structure 2030 for laserprocessing of the structure 2030. The pulsed beam 2021 interacts withthe third layer 2018 of structure 2010 without ablating a selectedportion 2022 thereof. Through the interaction with the laser pulses fromthe pulsed laser beam 2021 the conductivity of the selected portion 2022is changed to non-conductive. At the same time, a selected portion 2024of the first layer 2028 that is below the third layer 2018 does notexperience the same change in conductivity. Additionally, the selectedportion 2024 is not ablated by the beam 2021.

Conductive regions or layers are processed non-ablatively so they can beused in a touch-sensitive screen in electronic devices or in otherdevices related to printed electronics or optoelectronics, includingdevices benefiting from low damage, low visibility processing ofsubstrates or where precision is required. As used herein, “ablative”and “non-ablative” have meanings as presented above.

In some cases, the layers of conductive materials include a randomarrangement of silver nanowires. The silver nanowires of such layers canbe secured to a substrate in a polymer matrix, such as an organicovercoat. A laser beam can deliver laser pulses to such a layer andcreate a processed portion where the conductivity of the material ofconductive layer is substantially changed such that the processedportion is effectively non-conducting. As used herein, the terms“conductive” and “nonconductive” have meanings attributed to them thatare generally understood in the art of printed electronics, touch sensorpatterning, or optoelectronics, as set forth in greater detail below.

Laser pulses can be directed to the composite in various patterns suchthat particular regions and electrical pathways are formed on thesubstrate. By carefully selecting the characteristics of the laser pulseparameters, including pulse length, pulse fluence, pulse energy, spotsize, pulse repetition rate, and scan speed, the substrate may beprocessed such that electrical characteristics thereof are altered in apredetermined way while the substrate and associated protective andconductive layers are not substantially damaged or structurally altered(e.g., ablatively).

Exemplary laser pulse parameters suitable for non-ablative processing ofa conductive layer include a pulse length of about 50 ps, pulse fluenceof about 0.17 J/cm², a spot size of about 40 μm (1/e²), a scan rate ofabout 1 m/s with a pulse-to-pulse overlap of greater than 90%, a totalpulse energy of about 12 μJ, and a pulse repetition rate of about 100kHz, using optical radiation having a wavelength of 1064 nm (which hasbeen found to interact with the substrate and other materials to alesser extent than light of shorter wavelengths). Various otherparameters are also suitable. For example, pulse repetition rates can beincreased to 1 MHz, to 10 MHz, or to greater than 10 MHz to increaseprocessing speeds. Pulse length can be selected to be shorter or longer.Pulse fluence can be adjusted to ensure that the target is processednon-ablatively. Possible pulse lengths include less than about 1 ps, 100ps, 200 ps, 500 ps, 800 ps, or 1 ns. Other parameters can similarly bevaried and optimized accordingly. Laser parameters suitable fornon-ablative laser processing can be selected based in part on therelevant properties of the materials selected to be processed. Forexample, varying thickness of the substrate, the conductive layer, etc.,can affect how laser pulse heat is distributed or result in othertime-dependent effects requiring mitigation.

While beams for processing are generally brought to a focus at thestructure, other beam geometrical configurations and intensitydistributions are possible, including an unfocused beam, line beams,square or rectangular beams, as well as beams with uniform,substantially uniform or preselected intensity profiles across one ormore transverse axes. In some cases, a composite can be translated tohelp achieve geometrical features on its surface. In some cases, one ormore laser beams impinge on a composite from either a top or back sidedirection so that the beam propagates through the substrate to theconductive layer such that the beam causes ablative or non-ablativechanges to a conductive layer. In some cases, laser pulses cause aprocessed portion of a conductive layer to become non-conductive withoutchanging the visible characteristics of the processed portion.Similarly, laser pulses can process a conductive border eitherablatively or non-ablatively. Laser ablation of a conductive border canbe achieved by increasing the energy content of the laser beam incidenton the target surface. For example, the laser pulse parameters can beadjusted by increasing the pulse length, pulse fluence, total pulseenergy, by using shorter wavelengths, or by decreasing the spot size.Suitable laser systems capable generally include pulsed fiber lasers,pulsed fiber amplifiers, and diode pumped solid-state lasers.

IV. Patterning Conductive Films Using Variable Focal Plane to ControlFeature Size

In some cases, laser scanning systems can be used to process materialssuch as composite films for use in electronic devices (e.g., for use astouchscreens in electronic devices). In one exemplary processingscenario, one or more conductive materials (e.g., a layer of silvernanowires and a border of silver paste) can be deposited onto asubstrate, and a laser scanning system can be used to process theconductive materials (e.g., to reduce the conductivity of portions ofthe conductive layer, or to form various features through ablation ofthe material). The present disclosure provides various advantages overprior touchscreen fabrication processes, including screen printingand/or lithographic techniques. In particular, the present disclosureallows both a main body of a touchscreen and its IC raceways to beprocessed using a single laser scanning device.

Steps for processing a composite film can be configured so that touchsensitive regions for use in various display devices are formed in thecomposite film. Other suitable applications for processed materials caninclude display devices more generally, as well as LED phosphorenhancements, other commercial and consumer lighting applications,wearable electronics, and photovoltaic cells. However, composite filmsare particularly well-suited for mobile consumer displays, wherethinner, more durable, and more flexible formats are highly desirable.When used as a mobile consumer device display, it can be advantageousfor a composite film (and thus each layer of material making up thecomposite film) to be flexible and/or transparent. However, depending onthe intended use of the final product, it can be advantageous for acomposite film to be at least partially or highly opaque, and/or atleast partially or highly rigid. The systems, devices, and processesdescribed herein can be used to process composite films regardless oftheir transparency and/or rigidity. Composite films can be referred toherein simply as composites.

The substrate used can be formed from a variety of materials. Forexample, the substrate can be made of polyethylene terephthalate (PET)because of its low cost and advantageous features, includingtransparency, flexibility, resilience, ease of manufacture, etc. Anonexhaustive list of other possible substrate materials includespolyethylene naphthalate, polyurethane, various plastics, variousglasses, and various metals. The substrate can have various thicknesses.For example, the substrate can have a thickness between about 10 μm and1 mm, or between about 50 μm and 200 μm, or in one specific example,about 130 μm.

In some cases, a flexible and transparent composite material includes asubstrate (e.g., PET) with a layer of silver nanowires (also referred toas SNW or AgNW) deposited thereon to a predetermined thickness or to apredetermined conductivity, either of which can be achieved byincreasing or decreasing the density of the silver nanowires duringcomposite production. The layer of silver nanowires can have variousthicknesses, such as a thickness between about 1 nm and 100 nm, orbetween about 3 nm and 70 nm, or between about 30 nm and 50 nm. Silvernanowires are well-suited for flexible substrates, as their materialproperties, such as conductivity and structural integrity, are moreconsistent under bending loads of various types (e.g., fixedly curved,cyclically deformed, or pliable). In some cases, indium tin oxide (ITO)or other suitable materials can be used instead of silver nanowires.

FIG. 10 shows one embodiment of a laser scanning system 100. The system100 includes a source 102 of a laser beam 104, illustrated by a pair ofray lines 106, 108. The laser beam 104 propagates along an optical axis124, shown in dashed lines, from the source 102 to a focus-control lens110 that is retained by a housing 112. The lens 110 can be a singleoptical element such as a plano-concave or double concave lens, or acompound lens that includes two or more single lens elements. In mostcases, the focus-control lens 110 produces a diverging beam, but in someexamples, the focus-control lens 110 causes the beam 104 to initiallyconverge to a focus, then expand as it propagates away from the focus.Upon exiting the focus-control lens 110, the beam 104 is directed alongthe optical axis 124 toward an objective lens assembly 116, whichconverges the beam 104 as it exits the objective lens assembly 116. Theconverging beam is then directed toward a first reflective surface 118,which reflects the beam 104 toward a second reflective surface 120,which reflects the beam toward a substrate 122 at which the beam 104 isfocused at focal point 126. Typically, the beam 104 is focused at someportion of a substrate thickness, but beam focus can be in front of orbehind the substrate as well as within the substrate 122.

As shown in FIG. 10, the reflective surfaces 118, 120 of the system 100can be adjustable in order to steer the beam with respect the substrate122. As one example, the surfaces 118, 120 can be reflective surfacescoupled to first and second galvanometers 119, 121, respectively, andthus their orientations can be manipulated and controlled using acontrol system 140 that provides scan and focus control. The controlsystem 140 is also coupled to one or more galvanometers or other focusadjustment mechanisms 114 that displace the focus-control lens 110 alongthe axis 124. As shown in FIG. 10, the focus-control lens 110 can bemoved to a variety of positions, such as a position 115 shown in dashedlines. With such movements, the focus-control lens 110 provides an inputbeam to the objective lens assembly 116 so that the beam is focused atan acceptable location so as to compensate for non-flat focal planes orcurved and/or non-planar substrates.

While the focus-control lens 110 can adjust focus of the beam 104 at thesubstrate, large beam displacements along the axis 124 are generally notavailable. Instead, the housing 112 of the focus-control lens 110 issecured to a translation stage 130 so as to move the focus-control lens110 along the axis 124 to a variety of positions, such as a position 117shown in dashed lines. These relatively larger motions of the housing112 and the focus-control lens 110 permit an extended range over whichthe beam 104 can be focused, and thus permit corresponding variations inbeam spot size at a focus location. The substrate 122 is positionedalong the axis 124 with a translation stage 131 so that beams of variousspot sizes can be focused at the substrate 122. For convenientdescription, such adjustments of the focus-control lens 110 with thetranslation stage 130 can be referred to as beam diameter adjustments.

The system of FIG. 10 permits maintaining focus even across curved ornon-planar target surfaces. FIG. 11 illustrates focusing of an opticalbeam with a system such as the system 100. An objective lens 200 issituated to focus the optical beam along an axis 208. For a fixed lensposition, and a beam focus along the axis 208, the beam is generally notin focus across a plane 204 as scanned. Instead, the scanned beam focusdefines a curved surface 206. In order to focus on a flat substrate (orsubstrate of other shape), a focus-control lens is adjusted to establishbeam focus on the plane 204 (or other surface). As shown in FIG. 11,typically the greater the angle between ray directions and the axis 208(i.e., the larger the angle α2 is), the greater this displacement of theactual focus from the plane 204. To vary beam spot size, a focus-controllens is translated with, for example, a translation stage 130 as shownin FIG. 10. With such an adjustment, a beam can be focused with adifferent beam diameter at an alternative focal plane 214 using afocus-adjust lens to correct the curved field focal surface 216. In thismanner, beam focus is accomplished primarily with relatively smaller(and typically faster) focus adjustments while beam spot size isadjusted with relatively large (and typically slower) beam spot sizeadjustments.

In some systems, servomotors or other motion control devices (orpiezoelectric devices, galvanometers, translation stages, etc.) can besituated so as to move a focus-control lens to correct for fieldcurvature and maintain beam focus at a substrate. Additional servomotors(or piezoelectric devices, galvanometers, translation stages, etc.) canbe situated to move the focus-control lens to further adjust thelocation of beam focus along the optical axis, typically to adjust beamdiameter.

Referring generally to FIG. 12, a cross-sectional view is shown of three(typically pulsed) laser beams 302, 303, 304, each with selected laserpulse parameters, directed to a composite 300 and focused at differentcomposite features. As shown, the composite 300 includes a substrate 306having a lower portion 305 and a peripheral lip 307, a peripheralconductive border 308, and a layer 310 of conductive material depositedon a top surface of the substrate 306. In some examples, the substrate306 has a constant or fixed thickness, or can have a variable thickness,depending upon the application for which the composite is intended. Insome examples, the peripheral conductive border 308 comprises aconductive silver paste.

In some embodiments, the composite 300 can be processed to be used as acapacitive touchscreen in electronic devices. In such embodiments, thecomposite 300 can be transparent such that it can overlay the display ofan electronic device to provide touchscreen capabilities withoutimpeding a user's view of the display. The thin layer 310 can comprisethe main body of the touchscreen (i.e., it can overlay the display), andthe border 308 can comprise one or more integrated circuit (IC) racewaysto couple the ICs to the main body of the touchscreen. The ICs can beused to, for example, determine the location(s) of touch events on atouchscreen based on changes in capacitance(s) at various locations onthe touchscreen. The raceways couple the IC to the touchscreen itself toenable these determinations.

In various electronic devices, it can be desirable that the thin layer310 overlay the entirety of the device's display, in order to allow theuser to interact with the full extent of the display. Thus, it can benecessary to fit the IC raceways within the bezel of the electronicdevice. As electronic device bezels are made smaller, it can beadvantageous to similarly reduce the size of the IC raceways (so theycan fit within the bezel) and to be able to more finely control theirproperties (e.g., their conductivities and dimensions).

Because the border 308 and the thin layer 310 serve different purposes,they can be processed in different ways to achieve different results.For example, it can be advantageous to non-ablatively process the thinlayer 310 such that it maintains a uniform thickness and appearance to auser. However, it can be advantageous to ablatively process the border308 in order to form the IC raceways from the continuous border 308.Further, the planes z1, z2, and z3, on which the pulsed laser beams 302,304, and 303, respectively, are focused to process the layer 310 andborder 308, are separated from one another along the optical axes of thepulsed laser beams 302, 303, 304. Thus, the techniques described herein,which allow the processing of both the layer 310 and border 308 with asingle system, provide various advantages.

As explained above, FIG. 12 illustrates components of a composite beingprocessed by a laser patterning system such as the system 100. Inaccordance with the foregoing descriptions, the system 100 can be usedto process the thin layer 310 and the border 308 in a variety ofdifferent ways. For example, the system 100 can be employed tonon-ablatively process the thin layer 310, as explained in greaterdetail below. The system 100 can also be employed to ablatively processthe border 308, as also described in further detail below. In suchprocessing steps, movement of the focus-control lens 110 can beautomated to correct for field curvature. Movement of the housing 112can be controlled either manually or through a computer-controlled servomodule to control the location of the focal point of a laser beam in thedirection of the optical axis of the beam.

Thus, as shown in FIG. 12, a pulsed laser beam 302 can be controlled tobe focused on an exposed surface of the thin layer 310 at a focal planez1, in order to non-ablatively process the layer 310. Similarly, apulsed laser beam 304 can be controlled to be focused on an exposedsurface of the border 308 at a focal plane z2, in order to ablativelyprocess the layer 308. Further, in cases where a laser beam is used toablatively process the composite 300, the laser beam can be continuouslycontrolled so that it focuses at the surface of the material (which canmove as ablation occurs). In some cases, it is desirable to minimize thespot size of the laser beam on the surface it is processing. In suchcases, the focal plane of the laser beam is coincident with the exposedsurface of the material being processed, as illustrated for laser beams302 and 304. In other cases, however, larger feature sizes and thuslarger spot sizes may be used. In such cases, the focal plane of thelaser beam can be offset from the exposed surface of the material beingprocessed along the optical axis of the laser beam, as illustrated forlaser beam 303. Thus, the scanning laser systems described herein allowfor adjustment of feature sizes.

In some cases, a distance between a laser scanning system and a surfaceof a material to be processed can be adjusted to, for example, increasethe distance to provide a larger field size, to decrease the distance toimprove accuracy, or to vary focused spot size. Thus, in some cases, amaterial to be processed by a laser scanning system can be situated onan adjustable surface, which can be moved to adjust the distance betweenthe scanning system and the surface to be processed. For example, asshown in FIG. 12, the composite 300 can be situated on a platform 312,which can be adjustable along an axis ZF. Various mechanisms can be usedto adjust the platform 312 along the ZF axis. As one example, theplatform can be coupled to one or more threaded rods 314 threaded intorespective hollow tubes 316 having corresponding threads on innersurfaces. Thus, rotation of the tubes 316 causes motion of the platform312 and thus the composite 300 along the axis ZF. The tubes 316 can besupported on a base unit 318. Of course, any other translationmechanisms can be used as well.

FIG. 13 shows laser beams 406, 408, 410, each propagating alongdifferent axes as directed by a laser scanning system 412, which canhave a configuration similar to that of system 100. Each of the laserbeams 406, 408, 410, is shown in three different configurations (asbeams 406A, 406B, 406C or 408A, 408B, 408C, or 410A, 410B, 410C,respectively): in a first configuration focused on a first focal plane400A or 400B (i.e., as shown at 406A, 408A, and 410A), in a secondconfiguration focused on a second focal plane 402A or 402B (i.e., asshown at 406B, 408B, and 410B), and in a third configuration focused ona third focal plane 404A or 404B (i.e., as shown at 406C, 408C, and410C). Focal plane 400A is farther from the system 412 than focal plane402A by a distance x2, and focal plane 402A is farther from the system412 than focal plane 404A by the distance x3. The distances x4, x5, x6typically correspond to different focus locations corresponding to fieldcurvature in an objective lens. Thus, an objective lens may form a beamfocus for a target portion of a substrate situated on the objective lensaxis at the plane 400A; absent a focus adjustment, the beam incident toan off-axis target portion would be focused on the plane 400B. As notedabove, a focus-control lens can be provided to adjust focal position tocompensate.

Displacements x2, x3 are generally provided to correspond to largertranslations of a focus-control lens so as to produce beam spot sizechanges. The displacements x2, x3 are generally unequal, and a beam spotsize as focused at the plane 400A is typically larger than a beam spotsize at the plane 402A which is in turn larger than a beam spot size forfocus at the plane 404A. As shown in FIG. 12, a processing system isconfigured to provide focus adjustments (x4, x5, x6) at locationsassociated with different beam spot sizes (i.e., at displacements x2,x3).

FIG. 14 shows an exemplary method 500 for processing a composite such asa composite to be processed for use as a touchscreen in an electronicdevice. At 502, a composite that includes a substrate having aconductive layer and a conductive border formed thereon is selected. At504, a pattern or process description is obtained that indicates howvarious portions of the composite are to be processed, and can includepattern layouts, dwell times, feature sizes, types of processing (e.g.,ablation or other processes). At 506, processing beam parameters such apower, wavelength, pulse repetition rate, pulse energy, and beam spotsize are associated with the pattern description. At 508, focal planes(or working distances) are selected to produce the selected beam spotsizes. At 510, a focus-control assembly is positioned so that a beamfrom the focus-control assembly is focused to a suitable beam spot sizeat the selected focal plane. As shown in FIG. 14, the focal plane isselected for processing the conductive layer. At 512, the conductivelayer (or other substrate regions) is processed with the selected spotsize/working distance with focus control provided by a focus-controllens. At 514, a focus-control assembly is positioned so that a beam fromthe focus-control assembly is focused to another suitable beam spot sizeat another selected focal plane. As shown in FIG. 14, this focal planeis selected for processing the conductive border. At 516, the conductiveborder (or other substrate region) is processed with the selected spotsize/working distance with focus control provided by a focus-controllens. Processing terminates at 520. A plurality of different workingdistances and beam spot sizes can be used, based on the patterndescription. While a range of beam spot sizes can be used, such as beamdiameters of between 2 μm and 10 mm, 4 μm and 1 mm, 5 μm and 0.5 mm, or8 μm and 0.2 mm, typical beam spot sizes are between 10 μm and 100 μm.These beams can generally process composites that include conductivesilver paste or silver nanowires to have features of correspondingsizes.

Ablative and Non-Ablative Processing of the Conductive Layer and Border

In some cases, the conductive layer is processed non-ablatively so itcan be used as a touch-sensitive screen in electronic devices and theconductive border is processed ablatively so that it forms IC racewaysleading from the touch-sensitive screen to an integrated circuit. Inalternative embodiments, however, either the conductive layer or theconductive border can be either ablatively or non-ablatively processed,as is suitable for the particular embodiment. As used herein, “ablative”and “non-ablative” have meanings as presented above.

In some cases, the layers of conductive materials includes a randomarrangement of silver nanowires. The silver nanowires of such layers canbe secured to a substrate in a polymer matrix, such as an organicovercoat. A laser beam can deliver laser pulses to such a layer andcreate a processed portion where the conductivity of the material ofconductive layer is substantially changed such that the processedportion is effectively non-conducting. As used herein, the terms“conductive” and “nonconductive” have meanings attributed to them thatare generally understood in the art of printed electronics, touch sensorpatterning, or optoelectronics. For example, suitable sheet resistancesfor a material such that it may be considered conductive include 30-250Ω/sq, and suitable sheet resistances or electrical isolationmeasurements for a material such that the material may be considerednon-conductive or electrically isolated include resistances greater thanor equal to about 20 MΩ/sq. However, these sheet resistances are merelyexamples, and other conductive and non-conductive ranges may applydepending on the requirements of the particular application. Someprocessed substrates may be considered sufficiently conductive withsheet resistances below 500 Ω/sq, 1 kΩ/sq, 5 kΩ/sq, or 10 kΩ/sq, and maybe considered non-conductive with sheet resistances greater than orequal to about 100 kΩ/sq, 1 MΩ/sq, or 100 MΩ/sq.

Laser pulses can be directed to the composite in various patterns suchthat particular regions and electrical pathways are formed on thesubstrate. By carefully selecting the characteristics of the laser pulseparameters, including pulse length, pulse fluence, pulse energy, spotsize, pulse repetition rate, and scan speed, the substrate may beprocessed such that electrical characteristics thereof are altered in apredetermined way while the substrate and associated protective andconductive layers are not substantially damaged or structurally altered(e.g., ablatively).

Exemplary laser pulse parameters suitable for non-ablative processing ofa conductive layer include a pulse length of about 50 ps, pulse fluenceof about 0.17 J/cm², a spot size of about 40 μm (1/e²), a scan rate ofabout 1 m/s with a pulse-to-pulse overlap of greater than 90%, a totalpulse energy of about 12 μJ, and a pulse repetition rate of about 100kHz, using optical radiation having a wavelength of 1064 nm (which hasbeen found to interact with the substrate and other materials to alesser extent than light of shorter wavelengths). Various otherparameters are also suitable. For example, pulse repetition rates can beincreased to 1 MHz, to 10 MHz, or to greater than 10 MHz to increaseprocessing speeds. Pulse length can be selected to be shorter or longer.Pulse fluence can be adjusted to ensure that the target is processednon-ablatively. Possible pulse lengths include less than about 1 ps, 100ps, 200 ps, 500 ps, 800 ps, or 1 ns. Other parameters can similarly bevaried and optimized accordingly. Laser parameters suitable fornon-ablative laser processing can be selected based in part on therelevant properties of the materials selected to be processed. Forexample, varying thickness of the substrate, the conductive layer, etc.,can affect how laser pulse heat is distributed or result in othertime-dependent effects requiring mitigation.

While the beams are generally described as being brought to a focus,other beam geometrical configurations and intensity distributions arepossible, including an unfocused beam, line beams, square or rectangularbeams, as well as beams with uniform, substantially uniform orpreselected intensity profiles across one or more transverse axes. Insome cases, a composite can be translated to help achieve geometricalfeatures on its surface. In some cases, one or more laser beams impingeon a composite from either a top or back side direction so that the beampropagates through the substrate to the conductive layer such that thebeam causes ablative or non-ablative changes to a conductive layer. Insome cases, laser pulses cause a processed portion of a conductive layerto become non-conductive without changing the visible characteristics ofthe processed portion. Similarly, laser pulses can process a conductiveborder either ablatively or non-ablatively. Laser ablation of aconductive border can be achieved by increasing the energy content ofthe laser beam incident on the target surface. For example, the laserpulse parameters can be adjusted by increasing the pulse length, pulsefluence, total pulse energy, by using shorter wavelengths, or bydecreasing the spot size. Suitable laser systems capable generallyinclude pulsed fiber lasers, pulsed fiber amplifiers, and diode pumpedsolid-state lasers.

Exemplary Control System and Computing Environment

FIG. 15 shows an exemplary laser processing system that includes acontrol system 600 for controlling a laser beam delivery system 603. Asshown, the control system 600 can include a laser beam parameter controlinterface 602, a stage control interface 604, two galvanometer controlinterfaces 606 and 608 for controlling the scanning of a laser beam, andfirst and second stage control interfaces 610, 612. The laser beamparameter control interface 602 can be coupled to a source of a laserbeam such as source 605, and can control parameters of the laser beamgenerated thereby, such as pulse length, pulse fluence, pulse energy,pulse light wavelength, etc. Typically, the control system 600 includesone or more processors 607 and a memory 609 that retains pattern dataand instructions for processing pattern data for determining laser scanparameters. The control interfaces are typically implemented based oncomputer-executable instructions stored in one or more computer readablestorage media such as magnetic disks or memory such random accessmemory.

The stage control interface 604 can be coupled to a substrate stage 618,which can control the location of a composite to be processed. Thesubstrate stage 618 can comprise any of a variety of motion controldevices such as piezoelectric or motorized scanning devices. Thegalvanometer control interfaces 606, 608 can be coupled to galvanometers616, 614, respectively, which can control reflective surfaces 617, 615,respectively. The first and second stage control interfaces 610, 612,can be coupled to motion control devices 629, 630, respectively, and cancontrol linear motion of the stages along an optical axis. The motioncontrol device 629 is coupled to a focus-adjust assembly 628 so thatbeam focus can be maintained during beam scanning. The focus-adjustassembly 628 is secured to the motion control device 630 so as to selecta suitable beam diameter for substrate processing. One additionallocation of the focus-adjust assembly 628 is shown at 628A. Adjustmentsof the focus-adjust assembly 628 with the motion control device 630 aregenerally accompanied with corresponding movement of the substrate 618so that beam focus at a different beam diameter is achieved, while focusover a scan field can be maintained with the motion control device 629.

FIG. 16 depicts a generalized example of a suitable computingenvironment 700 in which the described innovations may be implemented.The computing environment 700 is not intended to suggest any limitationas to scope of use or functionality, as the innovations may beimplemented in diverse general-purpose or special-purpose computingsystems. For example, the computing environment 700 can be any of avariety of computing devices (e.g., desktop computer, laptop computer,server computer, tablet computer, media player, gaming system, mobiledevice, etc.)

With reference to FIG. 16, the computing environment 700 includes abasic configuration 730 including one or more processing units 710, 715and memory 720, 725. The processing units 710, 715 executecomputer-executable instructions. A processing unit can be ageneral-purpose central processing unit (CPU), processor in anapplication-specific integrated circuit (ASIC) or any other type ofprocessor. In a multi-processing system, multiple processing unitsexecute computer-executable instructions to increase processing power.For example, FIG. 16 shows a central processing unit 710 as well as agraphics processing unit or co-processing unit 715. The tangible memory720, 725 may be volatile memory (e.g., registers, cache, RAM),non-volatile memory (e.g., ROM, EEPROM, flash memory, etc.), or somecombination of the two, accessible by the processing unit(s). The memory720, 725 stores software 780 implementing one or more innovationsdescribed herein, in the form of computer-executable instructionssuitable for execution by the processing unit(s).

A computing system may have additional features. For example, thecomputing environment 700 includes storage 740, one or more inputdevices 750, one or more output devices 760, and one or morecommunication connections 770. An interconnection mechanism (not shown)such as a bus, controller, or network interconnects the components ofthe computing environment 700. Typically, operating system software (notshown) provides an operating environment for other software executing inthe computing environment 700, and coordinates activities of thecomponents of the computing environment 700.

The tangible storage 740 may be removable or non-removable, and includesmagnetic disks, magnetic tapes or cassettes, CD-ROMs, DVDs, or any othermedium which can be used to store information in a non-transitory wayand which can be accessed within the computing environment 700. Thestorage 740 stores instructions for the software 780 implementing one ormore innovations described herein.

The input device(s) 750 may be a touch input device such as a keyboard,mouse, pen, or trackball, a voice input device, a scanning device, oranother device that provides input to the computing environment 700. Forvideo encoding, the input device(s) 750 may be a camera, video card, TVtuner card, or similar device that accepts video input in analog ordigital form, or a CD-ROM or CD-RW that reads video samples into thecomputing environment 700. The output device(s) 760 may be a display,printer, speaker, CD-writer, or another device that provides output fromthe computing environment 700.

The communication connection(s) 770 enable communication over acommunication medium to another computing entity. The communicationmedium conveys information such as computer-executable instructions,audio or video input or output, or other data in a modulated datasignal. A modulated data signal is a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia can use an electrical, optical, RF, or other carrier.

Software 780 can include one or more software modules. For example,software 780 can include a laser beam software module 782 for settinglaser beam parameters and/or controlling a source of a laser beam, asubstrate stage motion module 784 for setting substrate position alongan axis and controlling a substrate stage, and a beam scanning module786 for determining parameters of a beam scanning system and/orcontrolling such a beam scanning system. One exemplary beam scanningsystem can include a pair of galvanometers. A focus control module 780can also include a field focus correction module 788 for determiningactions to be taken to correct for field curvature such as by motion ofa focus-adjust lens. A beam diameter module 790 can control movements tofocus a beam at a particular distance to obtain a selected beamdiameter.

Although the operations of some of the disclosed methods are describedin a particular, sequential order for convenient presentation, it shouldbe understood that this manner of description encompasses rearrangement,unless a particular ordering is required by specific language set forthherein. For example, operations described sequentially may in some casesbe rearranged or performed concurrently. Moreover, for the sake ofsimplicity, the attached figures may not show the various ways in whichthe disclosed methods can be used in conjunction with other methods.

Any of the disclosed methods can be implemented as computer-executableinstructions stored on one or more computer-readable storage media(e.g., one or more optical media discs, volatile memory components (suchas DRAM or SRAM), or nonvolatile memory components (such as flash memoryor hard drives)) and executed on a computer (e.g., any commerciallyavailable computer, including smart phones or other mobile devices thatinclude computing hardware). The term computer-readable storage mediadoes not include communication connections, such as signals and carrierwaves. Any of the computer-executable instructions for implementing thedisclosed techniques as well as any data created and used duringimplementation of the disclosed embodiments can be stored on one or morecomputer-readable storage media. The computer-executable instructionscan be part of, for example, a dedicated software application or asoftware application that is accessed or downloaded via a web browser orother software application (such as a remote computing application).Such software can be executed, for example, on a single local computer(e.g., any suitable commercially available computer) or in a networkenvironment (e.g., via the Internet, a wide-area network, a local-areanetwork, a client-server network (such as a cloud computing network), orother such network) using one or more network computers.

Furthermore, any of the software-based embodiments (comprising, forexample, computer-executable instructions for causing a computer toperform any of the disclosed methods) can be uploaded, downloaded, orremotely accessed through a suitable communication means. Such suitablecommunication means include, for example, the Internet, the World WideWeb, an intranet, software applications, cable (including fiber opticcable), magnetic communications, electromagnetic communications(including RF, microwave, and infrared communications), electroniccommunications, or other such communication means.

FIG. 17 illustrates a focus assembly 808 that is translatable to fixedpositions (such as 808A) based on assembly stops 810A-810C. A stage 802translates the focus assembly 808 along an axis 812 of an objective lens814. The focus assembly 808 includes a lens 806 that is translatablewithin the focus assembly 808 to adjust a beam focus locationestablished by the objective lens 814 so as to compensate fieldcurvature or non-planar substrates. One representative location of thelens 806 is shown at 806A.

V. Optimization of High Resolution Digitally Encoded Laser Scanners forFine Feature Marking

An important characteristic of laser scanning systems is the resolution(used herein to refer to the minimum distance between twodistinguishable points) they can achieve. Conventional laser scanningsystems have attempted to improve resolution by reducing the workingdistance between the laser scanner and the surface being scanned,resulting in smaller resolution scanning over a smaller scanning field.In order to maintain large-field scanning capabilities, the conventionalsystems have employed expensive translatable stages to translate thesurface being scanned, such that a plurality of small fields can bescanned adjacent one another on a surface to form a large field. Theseconventional systems have several deficiencies.

Previous laser scanning systems have typically used 16-bit laserscanners, reduced the working distance until a desired resolution isachieved, and then scanned a plurality of small fields, relying on atranslatable stage to move the surface being scanned relative to thescanner. It has been found that by using 20-bit scanners, improvedresolutions (e.g., by a factor of 16) can be achieved using similartechniques. Alternatively, it has also been found that by using 20-bitscanners, similar resolutions can be achieved at larger workingdistances, thereby reducing or eliminating the need to scan pluralfields and therefore the need to translate the surface being scannedrelative to the scanner. This provides several distinct and significantadvantages over conventional systems. For example, significantly smallerresolution scanning can be achieved. Further, by reducing or eliminatingthe need to stitch together many small scan fields, errors introduced inthe stitching process are reduced or eliminated.

FIG. 18 shows a digital laser scanning system 3000 (such as a 20-bitlaser scanning system) and laser beams 3008, 3010, and 3012, eachpropagating along different axes as directed by the system 3000. Each ofthe laser beams 3008, 3010, 3012 is shown in three differentconfigurations (as beams 3008A, 3008B, 3008C or 3010A, 3010B, 3010C, or3012A, 3012B, 3012C, respectively): in a first configuration focused ona first focal plane 3002 (i.e., as shown at 3008A, 3010A, and 3012A), ina second configuration focused on a second focal plane 3004 (i.e., asshown at 3008B, 3010B, and 3012B), and in a third configuration focusedon a third focal plane 3006 (i.e., as shown at 3008C, 3010C, and 3012C).Focal plane 3002 is farther from the system 3000 than focal plane 3004,and focal plane 3004 is farther from the system 3000 than focal plane3006.

The digital laser scanning system 3000 generally produces an angulardeflection α that is digitally specified by a predetermined number ofbits. For example, the digital laser scanning system 3000 can specifydeflection angles based on n bits, wherein n is an integer such as 8,16, 18, 20, or larger. An n-bit digital laser scanning system canidentify 2^(n) distinct deflection angles. A transverse displacement don a selected focal plane is generally proportional to a product of theangular deflection a and focal plane distance along an axis 3050. Atransverse displacement resolution (for a fixed angular deflectiondifference) is defined as the associated difference in transversedisplacement.

As shown in FIG. 18, the transverse displacement resolution at the focalplane 3006 is smaller than the transverse displacement resolution atfocal plane 3004, which is smaller than the transverse displacementresolution at focal plane 3002. That is, as the working distance fromthe system 3000 increases, transverse displacement resolution increases.Because focal plane 3002 is farther from the system 3000 than focalplane 3004 and focal plane 3004 is farther from the system 3000 thanfocal plane 3006, the transverse displacement resolutions x10>x11>x12.Using a 20-bit scanning system rather than a 16-bit scanning system,desirable resolutions can be achieved at working distances large enoughto allow the scanning of a scan field as large as one square meterwithout translating the scanned surface relative to the scanning systemand stitching plural smaller scan fields together to form a larger scanfield. More specifically, a 20-bit scanning system is capable ofscanning a one square meter scan field with a resolution of less thanone micrometer.

The system 3000 can include a laser configured to produce a processingbeam, an optical system, and a scan controller configured to receive ascan pattern and couple scan control signals to the optical system. Insome cases, the scan pattern can be defined as a plurality of scanvectors. In some cases, the scan control signals can control the opticalsystem to direct the processing beam to a scan area with a predeterminedbeam diameter. In some cases, the scan controller is configured tocouple scan control signals to the optical system to control the opticalsystem to scan the processing beam across, or with respect to, the scanarea, so as to produce at least one exposed scan vector. In some cases,a transverse offset between the exposed scan vector and an intended scanvector is less than 1/10, or less than 1/20, of the predetermined beamdiameter. In some cases, the scan control signals correspond to the scanvectors to within an accuracy of at least ½¹⁶ (0.0015%), such as about½¹⁷ (0.00076%), or about ½¹⁸ (0.00038%), or about ½¹⁹ (0.00019%), orabout ½²⁰ (0.000095%).

Table 1 shows more specifically the resolution achievable, in μm/bit,with a variety of scanning systems for several field sizes. Inparticular, Table 1 shows the specific advantages of the 20-bit scanningsystem over a 16-bit scanning system for square fields having sides ofdifferent lengths.

TABLE 1 Resolution as a Function of Given Field Sizes Square Field EdgeLength # Bits 0.1 m 0.25 m 0.5 m 0.75 m 1.0 m 1.2 m 10 98 244 488 732976 1172 12 24 61 122 183 244 293 14 6.1 15.3 31 46 61 73 16 1.53 3.817.6 11 15 18 18 0.38 0.95 1.9 2.9 3.8 4.6 20 0.095 0.2384 0.48 0.72 0.951.14 22 0.024 0.06 0.12 0.18 0.24 0.29 24 0.0006 0.015 0.03 0.04 0.060.072

FIGS. 19A and 19B show the resolution achievable with a 16-bit scanningsystem and with a 20-bit scanning system, respectively. The left imagesof FIGS. 19A and 19B show an input pattern of concentric circles, thelargest of which has a diameter of 1 mm. The right images of FIGS. 19Aand 19B show the patterns actually scanned by 16-bit and 20-bit scanningsystems, respectively, in response to the input pattern of concentriccircles. These patterns were scanned using the same optical system,laser, and scanner (operating in both 16-bit and 20-bit modes), ontophoto-sensitive paper. Based on the field size used in these examples,the transverse displacement resolution of the 16-bit scanning system was9.2 μm, and the transverse displacement resolution of the 20-bitscanning system was 0.6 μm. The results of these experiments clearlyillustrate the improved scanning resolution of the 20-bit scanningsystem. With higher transverse displacement resolution, shapes can betransferred to a substrate more accurately.

Thus, a 20-bit scanning system can provide smaller laser scribe lineswith smaller scanning pitches (used herein to refer to the smallestachievable center-to-center distances between features) than knownscanning systems, and can reduce quantization errors associated withbeam placement due to single bit accuracy limitations. In particular, toscan a 20 μm scribe line with a 40 μm pitch over a 0.5 m×0.5 m field, a16-bit scanning system provides only 5 to 6 bits (at 7.6 μm/bit) betweenscribe lines. Decreasing the scribe width to 10 μm and pitch to 20 μm, a16-bit system can provide only 2-3 bits between scribes, leading tosignificant quantization of beam placement and related errors (e.g., thespacing between features is less consistent). In contrast, to scan a 10μm scribe with a 20 μm pitch over a 0.5 m×0.5 m field, a 20-bit scanningsystem can provide between 41 and 42 bits between scribe lines,significantly reducing quantization effects. FIGS. 20A and 20Billustrate this improvement. FIG. 20A illustrates several lines scannedby a 16-bit scanning system at a 100 μm pitch and FIG. 20B illustratesthe same input pattern scanned by a 20-bit scanning system. Theimprovement in spacing consistency is visually discernible.

Further testing was conducted to evaluate improvements provided by20-bit scanning. FIG. 21 illustrates an input pattern scanned by both a16-bit and a 20-bit scanning system, with the numbers shown in FIG. 21indicating the pitch, in mm, of the associated pattern. The pitches ofthe scanned features were measured under high magnification, withresults presented in Table 2 for each of the patterns (either lines orcorners having a given spacing).

TABLE 2 Measured Pitches of Scanned Features 30 μm 50 μm 80 μm 100 μm70.7 μm 141.4 μm (Lines) (Lines) (Lines) (Lines) (Corners) (Corners) #Bits 16 20 16 20 16 20 16 20 16 20 16 20 Max 36.4 31.5 55.6 51.2 90.681.6 110.5 102 87.9 72.7 155.8 143.3 Meas. (μm) Min 26.8 28.9 41.2 49.473.4 78 85.6 97.6 59 69.4 127.7 139.4 Meas. (μm) Max − 9.6 2.6 14.4 1.817.2 3.6 24.9 4.4 28.9 3.3 28.1 3.9 Min (μm) Avg. 29.7 30.1 48.9 50.180.4 80.2 99.7 100 71.4 70.9 141.4 141.7 Meas. (μm) Std. 3.7 0.8 5.7 0.66.6 1 9 1.2 12 0.9 10 1.1 Dev. (μm)

Table 2 sets forth measurements of the pitches of scanned features,including the maximum spacings, minimum spacings, differences betweenthe minimum and maximum spacings, average spacings, and standarddeviations of spacings, for the six different patterns patterned withboth 16-bit and a 20-bit scanning. Spacings of corner features weremeasured on a diagonal between corners, and thus the nominal distancefor the features having a 50 μm pitch is 70.7 μm and the nominaldistance for the features having a 100 μm pitch is 141.4 μm. As shown inTable 2, 20-bit scanning had consistently and significantly betterperformance than 16-bit scanning. In particular, all standard deviationsof 20-bit measurements are within twice single bit resolution limits.

FIG. 22 illustrates an exemplary method 2200 by which materials can beprocessed. At 2202, a material to be processed by a laser scanningsystem is received. At 2204, a description of a pattern to be scannedonto the material is received. At 2206, the material is processedaccording to the pattern description using the laser scanning system andthe laser scanning system is operated so as to have 20-bit angularresolution. At 2208, processing terminates. In some cases, the method isused to process a scan field of at least one square meter with a singlelaser scanner and without translating the material with respect to thescanner.

Another exemplary method can include receiving a pattern descriptiondefining one or more pattern features, which can be associated withrespective scan vectors. The method can further include selecting alaser beam diameter and directing a laser beam having the selected or anotherwise predetermined beam diameter over a scan area of a substratebased on the pattern description. In some cases, the laser beam can bedirected over the scan area with a transverse displacement resolutionthat is less than 1/10 of the beam diameter. In some cases, the laserbeam can be directed over the scan area with a transverse displacementresolution that is less than 1/20 of the beam diameter. The scan areacan be square, rectangular, circular, or can have any other suitableshape.

Another exemplary method can include selecting a laser beam diameter(e.g., between about 10 μm and 100 μm), and situating a substrate on ascan plane at a desired working distance from a source of a laser beamsuch that the laser beam has the selected diameter at the scan plane. Insome cases, the scan plane can be associated with the selected laserbeam diameter, for example, the working distance can be determined basedon the selected diameter. The method can further include exposing thesubstrate to the laser beam by scanning the laser beam across, or withrespect to, the substrate. In some cases, the laser beam can be scannedwith angular scan increments corresponding to less than 1/10, or lessthan 1/20, or less than 1/100, or less than 1/1000 of the selected laserbeam diameter.

A 20-bit scanning system can improve resolution to such a degree thatthe scanning system is no longer the limiting factor in the achievableresolution. For example, equipment used to calibrate the scanning systemmay not be capable of calibrating to within the resolution achievable bythe scanning system. As another example, thermal and/or vibratoryeffects, as well as beam steering and/or material limitations mayintroduce errors larger than the resolution achievable by the scanningsystem. A 20-bit (or other) laser scanning system can use multi-pointextrapolation and averaging to place a beam across a scan field torealize further improvements over 16-bit encoding. Optical radiation ofany suitable wavelength or range of wavelengths, such as ultraviolet,visible, infrared, or other wavelengths can be used. In someembodiments, a laser scanning system can be used to scan atwo-dimensional surface such that the resolution of the scanning patternalong a first axis is the same as the resolution of the scanning patternalong a second axis. In alternative embodiments, a laser scanning systemcan be used to scan a two-dimensional surface such that the resolutionof the scanning pattern along a first axis is larger than the resolutionof the scanning pattern along a second axis.

The systems and methods described herein provide substantial advantages.For example, the systems and methods described herein can achieve moreprecise laser patterning of a material. The systems and methodsdescribed herein can allow laser patterning of a significantly largerscan field with similar or better resolution than prior systems andmethods. In particular, the systems and methods described herein canallow laser scanning of a scan field of larger than one square meterwith a resolution of less than one μm, without requiring translation ofmaterial and stitching of a plurality of scan fields to form a largercomposite scan field. This reduces or eliminates errors introduced bytranslatable stages and stitching processes. This also reduces the timeneeded to scan large fields, thereby reducing overall production time,and eliminates the need for expensive translatable stages, reducingoverall production costs.

In some embodiments, multiple 20-bit laser scanners can be used in anarray to simultaneously scan a surface to achieve even larger scanfields and/or even smaller resolution than with a single 20-bit scanner.This technique can further reduce the processing time required byprocessing multiple regions in parallel rather than in series (requiringadditional time for translation). In some embodiments, one or more20-bit laser scanning systems can be used to scan portions of a surfaceof a material, after which the material can be translated with respectto the one or more scanning systems (e.g., on one or more translatablestages) so the scanning systems can scan different portions of thesurface of the material. This technique can also be used to achieve evenlarger scan fields and/or even smaller resolution.

In embodiments in which multiple 20-bit scanning systems are used toscan multiple scan fields of a surface, and in embodiments in which a20-bit scanning system is used in combination with a translatable stageto scan multiple scan fields of a surface, multiple scan fields can bestitched together to form a larger composite scan field. For example, ifmultiple 20-bit scanning systems are used, each of the scanning systemscan be provided with a vision system, and the surface can be providedwith several fiducial marks placed in the field of view of the visionsystem. The vision system can use the fiducial marks to identify regionsof the surface the scanning systems have been assigned to scan and toalign scans from different scanning systems, if desired. As anotherexample, if a 20-bit scanning system is used in combination with atranslatable stage to scan multiple scan fields, the vision system canuse the fiducial marks to identify each of the multiple scan fields toalign the multiple scan fields to form a larger composite scan field.Because a 20-bit scanning system provides greatly improved resolution,multiple fields can be aligned (“stitched” together) with much greateraccuracy.

In some cases, computer systems can be provided with computer-executableinstructions stored in one or more computer readable media thatimplement computer-executable methods that optimize or otherwise arrangethe order in which vectors of a scan pattern are scanned by a laserscanning system. Such methods and systems can reduce the time requiredto scan a surface and thus overall processing time. Optimizationalgorithms used by such methods provide greater efficiency as numbers ofvectors in a scan pattern increases. Thus, it has been found that thesemethods are particularly valuable for large scan fields because largerscan fields typically include larger numbers of vectors to be drawn.

As noted above, 20-bit scanning systems can be used to process materialsto be used as capacitive touchscreens in electronic devices such as cellphones or tablets. In such embodiments, a large scan field can be usedto fabricate multiple touchscreens from a common substrate in a singlescanning session. A large scan field can also be used to fabricate largetouchscreens.

VI. Conclusion

In view of the many possible embodiments to which the principles of thepresent disclosure may be applied, it should be recognized that theillustrated embodiments are only preferred examples and should not betaken as limiting the scope of the disclosure. We claim all that comeswithin the scope and spirit of the appended claims.

We claim:
 1. A method, comprising: selecting a laser beam diameter;situating a substrate to be scanned at a scan plane associated with theselected laser beam diameter; exposing the substrate to a laser beamwith the selected laser beam diameter by scanning the laser beam withrespect to the substrate, wherein the laser beam is scanned with angularscan increments corresponding to less than 1/10 of the laser beamdiameter at the scan plane.
 2. The method of claim 1, wherein the laserbeam is scanned with angular scan increments corresponding to less than1/100 of the laser beam diameter at the scan plane.
 3. The method ofclaim 1, wherein the laser beam is scanned with angular scan incrementscorresponding to less than 1/1000 of the laser beam diameter at the scanplane.
 4. The method of claim 1, wherein the selected laser beamdiameter is between 10 μm and 100 μm.
 5. The method of claim 1, whereinscanning the laser beam with respect to the substrate comprises scanningthe laser beam over a fixed scan area of the substrate.
 6. The method ofclaim 5, wherein the fixed scan area is square or circular.
 7. Themethod of claim 5, wherein the fixed scan area is square and has an areaof at least one square meter.
 8. The method of claim 1, furthercomprising directing the laser beam over a fixed scan area of thesubstrate, wherein at least one of a laser beam power, pulse energy,pulse repetition rate, and laser beam diameter is selected so as toprocess the substrate.
 9. The method of claim 1, wherein the scanning ofthe laser beam is based on multi-point extrapolation and averaging. 10.An apparatus, comprising: a laser configured to produce a processingbeam; an optical system situated to receive the processing beam; and ascan controller configured to control the optical system to scan theprocessing laser beam with respect to a scan area of a substrate,wherein the processing laser beam is scanned with angular scanincrements corresponding to less than 1/10 of a processing beam diameterat the scan area.
 11. The apparatus of claim 10, wherein the processingbeam is scanned with angular scan increments corresponding to less than1/100 of the processing beam diameter at the scan area.
 12. Theapparatus of claim 10, wherein the processing beam is scanned withangular scan increments corresponding to less than 1/1000 of theprocessing beam diameter at the scan area.
 13. The apparatus of claim10, wherein the processing beam diameter is between 10 μm and 100 μm.14. The apparatus of claim 10, wherein scanning the processing beam withrespect to the scan area of a substrate comprises scanning theprocessing beam over a fixed scan area of the substrate.
 15. Theapparatus of claim 14, wherein the fixed scan area is square orcircular.
 16. The apparatus of claim 14, wherein the fixed scan area issquare and has an area of at least one square meter.
 17. The apparatusof claim 10, wherein the scan controller controls at least one of alaser beam power, pulse energy, pulse repetition rate, and theprocessing beam diameter so as to process the substrate.
 18. Theapparatus of claim 10, wherein the scan controller directs theprocessing beam based on multi-point extrapolation and averaging.
 19. Anapparatus, comprising: a laser configured to produce a processing beam;an optical system situated to receive the processing beam; and a scancontroller configured to control the optical system to scan the laserbeam with respect to a scan area of a substrate so as to produce anexposed scan vector, wherein a transverse offset between the exposedscan vector and an intended scan vector is less than 1/10 of a diameterof the laser beam at the scan area.
 20. The apparatus of claim 19,wherein the transverse offset between the exposed scan vector and theintended scan vector is less than 1/100 of the diameter of the laserbeam.